REL B3 Subwoofer static

I have a REL B3 subwoofer in my system that I leave on regardless of whether the entire system is on or not. Lately I have noticed that it is picking up a radio frequency and playing it through the woofer, sometimes loud enough to hear music and sometimes its just all static. I do not have an FM/AM antenna hooked up to my preamp or anywhere near the sub. I am sure it is a simple fix but before I tear apart my gear closet I'd like a little advice. Ground??????? Thanks